The invention relates to an electrically heated warming system for use in cold environments using rechargeable batteries as a source of electrical energy.
Many sports and activities are conducted outdoors under cold and possibly harsh conditions. Examples include snow skiing, hunting, ice skating, ice fishing, etc. Many occupations also involve exposure to similar conditions. In each circumstance, the body will respond to cold temperatures by directing blood flow to maintain core body temperature even though the extremities, hands and feet, may suffer discomfort.
A variety of products have been sold as sources of warmth for the extremities that may be used in boots, mittens, and gloves. Some of the products rely on slow chemical reactions that produce a range of heat output based on exposure to oxygen. Such products can be made inexpensively but are bulky and require a certain minimum rate of air flow or volume of air for proper operation. Chemical heat sources are not well suited for use in form fitting ski boots and typically are not designed to be reusable once depleted.
Another type of product relies on a battery current flowing through a resistive heat element to produce heat in the vicinity of the resistive element. Some products have a fixed current flow. Others have a variable rate of current flow. Both types of units, however, use batteries connected to the resistive element by a flat wire so that the battery pack is located outside the article of clothing. Battery packs for ski boots are often clipped on the back or outside of the boot by a spring clip.
Current versions of commercially available electrically heated insoles are thin and flat with an electrical heating element adhered at the forward end (at optimal toe placement) between a top layer of thin material and a cushioned bottom layer. See, U.S. Pat. No. 5,140,131 whose disclosure is herein incorporated by reference. A flat electrical cable ran beneath the insole from the heating element to the trailing edge beneath the cushioned layer, up the back of the boot between the inner boot and outer shell, and out the top to a battery clipped outside the boot. It was thought that a thin, flat insert, i.e., one free of anatomical features for providing contoured foot support, would be more desirable to avoid interference with the existing contoured insoles specifically made for relatively highly engineered ski and work boots. Adhesion of the heating element between the insole layers assured correct and secure placement of the element.
Unfortunately, there are some disadvantages to the conventional electrically heated thermal insoles. One is the trend towards more form-fitting ski boots that may become uncomfortable if even a thin thermal insole is added inside the foot chamber. Such close quarters in the foot chamber may also allow the users with some foot shapes to feel the flat cable running the length of the insole. Removal of the engineered insole reduces comfort. It would be desirable to have a heated insole for shoes, boots, and other footwear used in cold temperatures that could be customized to meet the size, shape, and support needs of almost any user for almost any activity.
What it gains in manufacturing quality and consistency with the thermal element, however, the conventional electrically heated thermal insole loses in flexibility. Retailers need to stock one complete thermal insole for each size boot they expect to sell. Because the thermal element and attached electrical cable is the more expensive component, ski boot retailer will need to make a significant investment in thermal insole inventory to be considered fully stocked for the entire range of ski boot sizes through any designated period in the skiing season. The user is also faced with an impossible choice: risk reduced comfort and fit for extended skiing time with the thermal insole rather than the original engineered insole for the boot.
It would be desirable to have a method for supplying an inventory of electrically heated thermal insole that could be stocked in a variety of sizes and in a quantity sufficient to supply cyclical business demands with minimum capital investment in inventory.
It would also be desirable to have an electrically heater thermal insole design that would exhibit a construction design that would provide the user and the retail seller with a quality product and options not available with conventional pre-constructed thermal insoles.
Electrically heated thermal insoles according to the invention are in the form of a kit made of separate packages for (a) a flexible, electrically powered resistance heating assembly that contains the heating element electrically bonded to a flexible power cable which terminates in a power supply connector, and (b) a flexible, cushioned footwear insole of extended length with a toe end and a heel end and having an upper layer bonded to a cushioned bottom layer, wherein the cushioned bottom layer exhibits a flap opening and a channel extending from the flap opening to the heel end of the insole for guiding the flexible power cable along the length of the insole. The inside of this flap is dimensioned to receive the heating element of the heating assembly and is covered with an adhesive which is, in turn, covered with a removable barrier film whereby insertion of the heating element, removal of the barrier, and closure of the flap opening will seal the heating element in the insole.
Electrically heated thermal insoles according to the invention are provided in the form of separate packages for the universally-sized heating assembly and for the sized insole. This separation of heating element and insole allows the retailer to stock a relatively few number of heating elements and a wide variety of relatively inexpensive sized insole units which may have the conventional flat profile for general use or may be contoured for an engineered fit for a particular type of footwear or foot shape. When the proper insole is selected, the user or the retailer install the heating element within the insole by introducing the heating element into the opening created by the insole flap, removing the barrier film to expose the adhesive, and sealing the heating element within the insole. When the heating element and power cord are aligned properly, the power cord lies in an outer channel formed into the bottom outside surface of the cushioned insole and extends from the embedded heating element to the heel end of the insole, up the back of the shoe or boot, and to an electrical connector suitable for forming a mated electrical connection with a control pack containing a battery, the mating electrical connector, and, preferably, an adjustable rheostat.
The heated insole kit and components of the invention offer advantages not previously available. With the kit of the present invention, retailers can reduce their investment in inventory by stocking a relatively limited number of universally-sized heating element assemblies and a wide variety of insoles of different sizes and shapes for more a precise matching to the user""s particular needs. Users receive a heated insole product that fits better and is better suited to their cold weather sporting needs.